Generally, electrical contact can be made to wafers or dies within packages, such as within a package-on-package (POP), by first applying a photoresist over the wafers or dies. The photoresist may then be patterned in order to expose portions of the wafers or dies to which contact is desired to be made. The patterning may be performed by exposing the photoresist to a radiation such as light in order to activate photoactive chemicals that may make up one component of the photoresist. A positive developer or a negative developer may then be used to remove either the exposed photoresist (for a negative development) or to remove the non-exposed photoresist (for a positive development).
Once the photoresist has been developed and patterned, electrical connections to the exposed wafers or dies may be formed by forming conductive material into the patterned photoresist such that an electrical connection is made. The conductive material may be formed by first applying a seed layer over the photoresist and along the sidewalls of the patterned photoresist. The seed layer may then be utilized, for example, in an electroplating process in order to plate the conductive material over and into the patterned photoresist, thereby providing the desired electrical connection to the underlying wafer or die.
However, because seed layers are utilized to form the conductive material, a problem can arise if gaps or other issues regarding the step coverage of the seed layer occurs. These gaps can be especially prevalent along the sidewalls of the photoresist if sputtering is performed to form the seed layer and the photoresist has a vertical sidewall. These gaps could, in turn, could cause gaps, uneven plating, or other problems to occur while the seed layer is used as an initiator for the subsequent plating of the conductive material.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.